HP 3000 Manuals

HP RXForecast Users Manual for MPE Systems

Seasonality 

Seasonality refers to a pattern of variation in data that is related to
specific time intervals (seasons).  If your company is on a 5-day work
week, you will see day-of-week seasonality because your systems do
little, if any, work on the weekends.  Firms that process orders often
experience week-of-month seasonality as the month-end approaches and
sales quotas must be met.

Follow the steps below to see how seasonality appears on a forecast.
First, change options on the RXForecast Options command dialog box:

   1.  Select an Interval Type of None.

       This will remove the interval bounds from the graphs.  You can
       better see the effects of enabling and disabling seasonality on
       forecasts with fewer lines on them.

   2.  Leave all Seasonality Levels checked.

   3.  Close this dialog box by clicking on  OK.

On the Forecasts command dialog box, do the following:

   1.  Change the metric to Global CPU.

   2.  Click on  OK.

You will see the following graph:


          Graph with All Seasonality Levels Checked 

This graph shows week-of-month seasonality.  Notice that every month
there is an increase in percent CPU utilized that is followed by a
decrease.

The program calculated a forecast including all seasonality levels since
you had left them all checked.  Because you also had enabled Auto Season,
it then checked to see if any seasonality was significant.  Only
week-of-month seasonality proved significant.  It then recalculated the
forecast using only week-of-month seasonality.

Close the graph.

Now draw the same graph with one difference:  uncheck every Seasonality
Level on the RXForecast Options command dialog box.

Produce the graph again and note the difference from the previous graph.


            

This graph draws no seasonality levels.  If you studied the data,
however, you would detect week-of-month seasonality.  You will generally
find it easier to let HP RXForecast detect and depict seasonality for
you.

Close the graph.

Try one more forecast.  This time, draw a forecast with a prediction
interval and seasonality.  Return to the RXForecast Options command
dialog box.

   1.  Enable all seasonality levels.

   2.  Select Prediction Interval.

Change nothing on the Forecasts command dialog box.  Just click on  OK to
draw the following graph:


            

Note that the interval shows the same pattern as the forecast.

For more information about the options on the RXForecast Options command
dialog box, see the entries for each option in Chapter 7 .

Close the graph.

MPE/iX 5.0 Documentation